Flange weld technique

ABSTRACT

A technique for securing a tube to a flange includes the steps of inserting the end of the tube into an aperture provided on the flange from the first side of the flange such that a portion of the tube extends at least to, and preferably beyond the second side of the flange opposite the first side. A ceramic plug is optionally inserted into the end of the tube to prevent weld spatter and tube burn-through. The tube is then welded to the flange about the circumference of the tube from the second side of the flange, and that portion of the tube which extends beyond the second side of the flange is removed by grinding to produce the finished product.

BACKGROUND OF THE INVENTION

The present invention is directed to the field of flanges connected topipes, and more particularly to a technique for welding pipes,especially manifold pipes to a flange.

In preparing exhaust manifolds and other gas carrying pipes in internalcombustion engines, it is usually necessary to provide at least one endof such pipes with a flange which is adapted to be connected to astructure such as an engine head.

More specifically, an exhaust manifold, for example, is usually providedwith a common flange connected to the ends of the exhaust pipes or tubesto thereby facilitate the connection of the tubes to the engine head.Typically, in preparing an exhaust manifold, it has been the practice toweld the manifold tubes to the flanges on the "tube side" of the flange,as opposed to the "head side" of the flange, since welding at the latterlocation would produce a rough surface and a significant amount of theweld material would project into the exhaust port, thus restricting theflow passages.

Unfortunately, welding the manifold to the flange from the tube side ismade difficult by the arrangement of the tubes in the manifold.Specifically, it is necessary to provide a weld about the entirecircumference of each tube. Since there are usually a number of tubeswhich extend from the engine head to the manifold collector, adjacenttubes interfere with each other during welding. The welding about theentire circumference of each tube from the tube side is thus renderedrelatively difficult, expensive and time consuming. Also, anundesireable gap between the tube and the flange, on the head side ofthe flange, will result when this technique is employed.

OBJECTS AND SUMMARY OF THE INVENTION

It is therefore an object of the invention to overcome the difficultiesassociated with the prior art welding technique.

It is a further object of the invention to provide a technique forwelding a tube to a flange on the side of the flange opposite the tube.

It is a further object to provide a low cost and rapid technique forwelding a tube to a flange.

Briefly, a first aspect of the present invention is directed to a methodfor securing a tube to a flange comprising the steps of inserting theend of the tube into an aperture provided on the flange from a firstside of the flange such that the tube extends at least to the surface ofthe second side of the flange opposite the first side. The tube is thenwelded to the flange about the circumference of the tube from the secondside of the flange. Any weld material which is deposited on the secondside of the flange is then removed to produce the final product.

Specifically, the aperture may be provided with a diameter such that agap, b, exists between the tube and the flange when the tube is insertedinto the aperture. A chamfer may also be provided at the intersection ofthe aperture and the second side of the flange, the chamfer having anangle, α and extending into the flange to a depth, c.

The step of inserting may include the step of inserting the end of thetube into the aperture such that a portion of the tube extends beyondthe second side of the flange by distance, a, and the step of removingmay include the step of removing the portion of the tube which extendsbeyond the second side of the flange.

In accordance with the preferred embodiment, the distance, a, is about1/4 inch, the gap, b, is about 0.06 inch, the angle, α, is approximately45° and the depth, c, is approximately 0.09 inch.

The step of welding may be accomplished through the use of a consumableelectrode welder and the step of removing the portion of the tube whichextends beyond the flange may be achieved through grinding. The methodmay further include the step of spot welding at least a portion of thetube to the flange from the first side of the flange prior to weldingfrom the second side of the flange in order to hold the tube and theflange in relatively fixed positions.

In accordance with a second aspect of the present invention, a methodfor securing a tube to a flange includes the steps of inserting the endof a tube into an aperture on a flange from a first side of the flangesuch that the tube extends at least to the surface of the second side ofthe flange. A plug is then inserted into the end of the tube and thetube is welded to the flange about the circumference of the tube fromthe second side of the flange while the plug is in the end of the tube.The plug is then removed from the tube and any weld material depositedon the surface of the second side of the flange is removed.

Specifically, the plug may be made of a refractory material, preferablyceramic. The plug is adapted to fit tightly into the end of the tube andhas a cross-section substantially identical to the cross-section of thetube. The plug may be provided with a protruding flange at the topthereof to prevent the plug from being inserted too far into the tubeand the plug may be provided with means at top thereof for facilitatingthe removal of the plug from the tube.

The present invention is also directed to a tube secured to a flange inaccordance with the above-described methods.

In accordance with a third aspect of the invention, a plug is adapted tobe disposed within the end of a hollow tube during the welding of thetube about its circumference to a flange through which it extends. Theplug is made of a refractory material and has a cross-section anddimensions substantially identical to the interior of the tube so as tofit tightly therein. The plug is preferably provided with a protrudingflange at the top thereof to prevent it from being disposed too farinside the tube and means on the top of the plug for facilitating theremoval of the plug from the tube.

In accordance with the fourth aspect of the invention, a tube and flangecombination comprises a flange, a tube and an interface portionconnecting the tube to the flange. The flange is provided withsubstantially planar top surface and an aperture therethrough. The tubeextends through the bottom surface of the flange to the top surface ofthe flange, the end the tube being substantially disposed in the planeof the top surface of the flange. The interface portion connects thetube to the flange at the aperture of the flange. The interface portioncomprises (i) a chamfer in the flange at the intersection of the topsurface and the aperture, (ii) weld material disposed between the tubeand the flange at the chamfer. The weld material functions to fasten thetube to the flange and has a top weld surface substantially disposed inthe plane of the top surface of the flange. The above combination mayfurther include a gap between the tube and the flange underneath theweld material.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and aspects of the invention will be describedin more detail with reference to the following drawing figures of which:

FIG. 1 is a perspective view of an exhaust manifold having a flangesecured thereto as seen from the tube side of the flange;

FIG. 2 is a perspective view of a portion of the flange illustrating theconnection between one of the tubes of the exhaust manifold and theflange produced according to the prior art welding technique, as viewedfrom the head side of the flange;

FIG. 3 is a perspective view of a portion of the flange illustrating theconnection between one of the tubes of the manifold and the flangeproduced according to the present invention, as viewed from the headside of the flange;

FIGS. 4-6 illustrate the process for welding each manifold tube to theflange in accordance with the present invention; and

FIGS. 7 and 8 illustrate the optional step of inserting a ceramic pluginto the tube prior to welding.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, exhaust manifold 10 is adapted to be securedto the head of an engine (not shown) through the use of flange 12 whichis adapted to be placed directly on a complementary surface on theengine head and bolted thereto by conventional means. The exhaustmanifold 10 as shown in FIG. 1 is comprised of three exhaust pipes ortubes 14 and a common pipe or tube 16 which is sometimes referred to asa collector. Although an exhaust manifold of the type illustrated inFIG. 1 will be employed in the following discussion, it will be readilyapparent to those skilled in the art that other types of structures,such as "header" type exhaust manifolds, thermal reactors, and the like,may readily employ the techniques of the present invention.

Also indicated in FIG. 1 is what will hereinafter be termed the "tubeside" 18 of the flange 12, which is opposite the "head side" 20 of theflange. FIG. 2 illustrates one of the tubes 14 and an associated sectionof the flange 12 from the head side 20 thereof. The prior art techniquefor securing the tube 14 to flange 12 would be to weld the tube 14 aboutits circumference to flange 12 from the tube side 18 of the flange sinceto weld from the head side 20 would produce a rough flange surface andports 15 could be obstructed by weld material. However, welding from thetube side results in a gap 22 between the tube 14 and flange 12. Thus,the end product produced by the prior art welding technique is notoptimum from an aesthetic point of view, and the total sealing surfacearea provided between the flange and the head is reduced by the area ofthe gap 22 thus reducing the quality of the seal between the head andthe flange. Further, those skilled in the art will appreciate thatwelding about the entire circumference of tube 14 from the tube side 18of the flange 12 is cumbersome, especially where multiple tubes areinvolved, as shown in FIG. 1, for example.

The tube-to-flange connection produced by employing the technique of thepresent invention is illustrated in FIG. 3. As shown therein, there isno gap between tube 14 and flange 12, the head side 20 of the flange 12forming a smooth and gap free interface with the tube 14. The totalsealing surface area provided between the head and the flange is thusmaximized. Additionally, the tube 14 is welded to the flange 12 from thehead side 20 of the flange to thereby greatly facilitate the weldingoperation. The technique for producing such connection will be describedwith reference to FIGS. 4-6.

With specific reference to FIG. 4, tube 14 and flange 12 are shown incross-section. The flange 12 is provided with an aperture 24 throughwhich tube 14 may extend by an approximate distance, a. The aperture isprovided with a diameter slightly greater than the outer diameter of thetube 14 to produce a gap, b, therebetween, and the head side 20 of theflange is provided with a chamfer 26 about the circumference of theaperture 24. The chamfer 26 is provided at an angle, α, relative to tube14, and extends downwardly to a depth, c.

After positioning the tube 14 relative to the flange 12 as shown in FIG.4, a few spot welds on the tube side 18 may be optionally employed torelatively fix the positions of the tube and flange if desired. The tubemay then be welded to the flange about its entire circumference from thehead side 20 of the flange. By extending the tube 14 beyond the headside 20 by the distance, a, the tube acts as a dam for the weld materialto thereby eliminate any weld bead from entering the port area 15.However, in applications where weld spatter on the ID of the tube isunimportant, the tube need only extend to the surface of the flange andnot beyond (a=o). The use of the chamfer 26 and gap, b, allow the weldmaterial to penetrate well below the surface of the head side 20 of theflange to thereby ensure a solid and secure connection between the tubeand flange.

Generally, the distance, a, will usually be up to approximately 1/2 ofan inch, and the gap, b, will usually be between approximately 0.01 inchand 0.1 inch. The angle, α, will usually be between approximately 20°and 60°, and the depth of the chamfer, c, will be between approximately0.01 inch and 0.15 inch.

In accordance with a specific example, the distance, a, that the tubeextended beyond the head side 20 of the flange was approximately 0.25inch, the clearance, b, between the tube 14 and the flange 12 wasapproximately 0.060 inch, and the chamfer was provided with an angle, α,of approximately 45°, to a depth, c, of approximately 0.090 inch.

The specific weld technique employed will be a function of the materialsused in the tube 14 and flange 12, as is well known in the art. Inaccordance with the above example, stainless steel was employed as thetube material, while the flange 12 consisted of carbon steel. A 20.5volt, 205 amp., 220 inch per minute wire speed was employed in aconsumable electrode welder. A slight gun angle (push) of approximately2° was employed and the wire was concentrated on the heavier flangematerial. The weld speed was approximately 32 inches per minute, and ashield gas of 98% argon and 2% oxygen was employed at a 35 cubic feetper hour rate. The particular wire employed is designated 0.045 ER 409C_(b).

Returning to FIG. 5, after welding, the weld bead 28 extends about theentire circumference of the tube 14 and is disposed between the tube 14and the flange 12, extending downwardly a sufficient distance into thegap to ensure a solid and secure connection between the tube and theflange. The portions of the tube 14 and weld bead 28 which extendupwardly beyond the head side surface of the flange 12 may be removed byany convenient grinding technique, such as blanchard grinding, surfacegrinding or milling, to produce the final product illustrated in FIGS. 3and 6. Of course, if the tube did not originally extend beyond theflange surface, only the weld bead would be ground. As shown in FIG. 6,the interface 30 between the tube 14 and the flange 12 is smooth, freefrom irregularities and secure. Since the weld bead and tube materialare typically stronger and more durable than the flange material, thesealing surface will be especially strong at the interface 30 where itis most needed. Additionally, since the welding is accomplished on thehead side 20 of the flange, the welding is less complicated, quicker andless expensive than the prior art since there is no interference betweenthe tubes.

An optional step in accordance with the present invention employs theuse of a plug 32 as shown in FIGS. 7 and 8. The plug 32 is inserted intotube 14 prior to welding in order to further prevent welding spatter onthe interior portions of the tube and to prevent burn-through of thetube 14 during the welding operation. Specifically, plug 32 ispreferably made of a ceramic or other refractory material and has across-section substantially identical to the shape of the tube, i.e.round for a round tube and square for a square tube. The dimensions ofthe plug are such that it fits tightly into the tube and extendsdownwardly into the tube well beyond the area of welding. The plug 32may be provided with an outwardly extending flange 34 at the top thereofadapted to prevent the plug from being inserted too far into the tube,and an eyelet 36, or other device at the top of the plug to helpfacilitate the removal of the plug from the tube. Since there is nopossibility of welding spatter ocurring on the inside of tube 14, any IDgrinding operations are completely eliminated. Additionaly, the use ofthe ceramic plug 32 prevents burn-through of the tube 14 at the point ofthe weld, since the ceramic material will function to dissipate heatfrom tube 14.

As shown in FIG. 7, the plug 32 is inserted into the tube 14 prior towelding, and is kept there through the welding operation as illustratedin FIG. 8. After welding, the plug may be removed to produce theintermediate product illustrated in FIG. 5. The portion of the tube 14extending beyond the flange may then be removed as discussed withreference to FIG. 6. However, if desired, the tube need only extendthrough the aperture to the surface of the flange and not beyond (a=o),in which case only the weld material need be ground off, since the plugwill prevent weld splatter from entering the tube.

In fabricating the exhaust manifold illustrated in FIG. 1, or anymulti-tube structure, the above-described method may be practicedsimultaneously on all such tubes connected to the flange, orindividually, as desired. That is, each tube may be positioned, weldedand ground substantially at the same time as the other tubes, or eachtube may be treated individually.

As will be appreciated by those skilled in the art, the above-describedtechnique may be used in many applications other than the fabrication ofan exhaust manifold, the present technique readily lending itself to thefabrication of virtually any flange for a pipe fitting. Althoughillustrated and described as being round, the tube may have virtuallyany cross section, such as square, oval, rectangular, etc., as desired.The distances, dimensions and angles discussed with reference to FIG. 4may readily be modified by those skilled in the art in order to achieveany particular effect as desired. Further, the specific weld techniquediscussed above is forth merely as an example, many other types ofwelding also being available as a matter of choice. Such modificationsare intended to be fully within the scope and spirit of the presentinvention.

Although the present invention has been described with reference to theforegoing specification and drawings, the scope of the invention willnow be defined with reference to the following claims.

What is claimed is:
 1. A method for manufacturing an exhaust manifoldfor mounting on an engine head, said method comprising:providing aflange having opposed first and second sides and at least one aperturetherein, said flange being defined by a chamfer at the intersection ofsaid aperature and said second side, said chamfer having an angle ofbetween approximately 20° and approximately 60° and extending into saidflange to a depth of between approximately 0.01 inch and approximately0.15 inch; providing at least one tube dimensioned to fit in saidaperture such that a gap of between approximately 0.01 inch andapproximately 0.1 inch exists between said tube and said flange;inserting one end of said tube into said aperture from the first side ofsaid flange such that said tube extends beyond the surface of the secondside of the said flange a distance of up to approximately one-half inch;welding said tube to said flange about the circumference of said tubefrom the second side of said flange; and removing any weld material fromthe surface of the second side of said flange and removing the portionof the tube which extends beyond the second side of said flange, wherebythe portion of said tube extending beyond said flange substantiallyprevents weld material from entering said tube during said welding, andwhereby the removal of said portion of said tube enables proper mountingof said flange on the engine head.
 2. The method of claim 1 wherein saidstep of welding comprises welding with a consumable electrode welder. 3.The method of claim 1 wherein said step of removing comprises grindingoff said portion of said tube.
 4. The method of claim 1 furthercomprising the step of spot welding at least a portion of said tube tosaid flange from the first side of said flange prior to the step ofwelding about the circumference of said tube from the second side ofsaid flange.
 5. The method of claim 1 further comprising the steps ofinserting a plug into the end of the tube after the tube has beeninserted into the flange and removing the plug from the end of the tubeafter the tube has been welded to the flange.
 6. The method of claim 3wherein said step of inserting a plug comprises inserting a plug made ofa refractory material.
 7. The method of claim 6 wherein said refractorymaterial comprises ceramic.
 8. The method of claim 6 wherein said stepof inserting a plug comprises inserting a plug which fits tightly intothe end of the tube.
 9. The method of claim 8 wherein the step ofinserting a plug further comprises inserting a plug having across-section substantially identical to the cross-section of the tube.10. The method of claim 9 wherein the step of inserting a plug furthercomprises inserting a plug having a protruding flange at the top thereofto prevent the plug from being inserted too far into the tube.
 11. Themethod of claim 10 wherein the step of inserting a plug furthercomprises inserting a plug having means at the top thereof forfacilitating the removal of the plug from the tube.
 12. An exhaustmanifold made in accordance with the method of claim 1.